A substantial number of the contemporary xerographic office copiers and the like have developed around the use of a cylindrical drum having a photoconductive surface thereon. The xerographic processing elements associated with such drums have developed to a relatively high degree of sophistication and reliability, but in many cases, in configurations which require the processing elements to interface with the peripheral surface of the photoconductor drum. Typical processing elements so configured include developers, paper path guiding arrangements, transfer apparatus, coronas, and so forth. Unfortunately, cylindrical drums, to retain the complete original document image, must be of such a diameter that they dictate the minimum size that an office copier can assume. Furthermore, the drum mounting structure requires relatively close tolerances to minimize variations in the drum photoconductive surface orientation, relative to the processing elements, as the drum rotates.
Although many contemporary copiers incorporate drum-type photoconductors, the use of flexible belts having a photoconductive external surface for the copying process has been known for many years. Sometimes these flexible belts have been used for accommodation of multiple images concurrently present on the photoconductor belt, such as is shown in the April 1967 IBM TECHNICAL DISCLOSURE BULLETIN (Vol. 9, No. 11) at pages 1526-1527 in the article entitled "An Electrographic Printer With Asynchronous Image Belt", by Hider and Medley. Other prior art flexible belt copiers have been employed for the purpose of positioning the photoconductive belt so that a flat portion thereof is located in a manner that will allow imaging of an entire document at one time, as is shown in U.S. Pat. No. 3,435,693 by Wright et al. wherein three rollers are employed to retain the flexible photoconductor belt in position, and U.S. Pat. No. 3,697,160 by Clark wherein two rollers provide the same function.
None of the known prior art flexible belt copiers have suggested configuring the belt mounts so as to accommodate the interface of processing elements designed and proven for use with cylindrical drums. Furthermore, none of the known prior art belt type copiers use an arrangement of the belt, its mount and the associated processing elements for maximum utilization of internal machine space in a manner that allows the most compact overall copier configuration.